Multispeed power tool transmission

ABSTRACT

A power tool with a housing, an electric motor having an output shaft that provides a first output torque, a first gear reduction element driven by the output shaft to provide a second output torque, a second gear reduction element, which can be operated in active and inactive modes, driven by the first gear reduction element to receive the second output torque and to provide a third output torque, a third gear reduction element, which is operable in active and inactive modes, driven by the first gear reduction element to receive the second output torque and to provide a fourth output torque, an output spindle operably driven by the second gear reduction element or the third gear reduction element, and a shift actuator. The shift actuator is employed to position the second and third gear reduction elements to achieve at least three overall speed ratios.

PRIORITY & CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.10/792,659 filed on Mar. 3, 2004, which is a continuation-in-part ofU.S. application Ser. No. 10/384,809 now U.S. Pat. No. 6,984,188 filedMar. 10, 2003, which is a divisional of U.S. application Ser. No.09/964,078 filed Sep. 26, 2001 entitled First Stage Clutch, now U.S.Pat. No. 6,676,557, which claims the benefit of U.S. ProvisionalApplication No. 60/263,379, filed Jan. 23, 2001. U.S. application Ser.Nos. 10/792,659 and 10/384,809 are incorporated by reference as if fullyset forth in their entirety herein.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates generally to power tools such as rotatabledrills, power screwdrivers, and rotatable cutting devices. Moreparticularly, the present invention relates to a transmission for amulti-speed transmission for a rotary power tool.

2. Discussion

Modernly, manufacturers of power tools have introduced rotary powertools that have variable speed motors in an attempt to permit the usersof these tools with sufficient control over the output speed of the toolso as to permit them to perform diverse operations without resort toadditional, specialized tools. Many of the tools that are commerciallyavailable include a three-stage, two-speed transmission that permitseven greater control over speeds of these tools.

Typically, the known transmission arrangements have lacked atransmission arrangement that could produce a wide range of outputspeeds and torques that would permit the tool to perform diverseoperations such as drilling holes with a large diameter hole saw,installing drywall screws or large diameter lag screws, and performinghigh-speed drilling operations. The single or dual speed transmissionsthat were generally employed in these tools typically did not havesufficient speed reducing capacity to permit these transmissions to bediversely employed as configuring these tools for high torque operationstended to impair their high speed performance. Furthermore, therechargeable batteries that were employed in many of the early cordlessrotary power tools were not well suited for use in low-speed, hightorque operations due to the amount of energy that is consumed and therate with which the energy is consumed by the power tool during suchoperations. Consequently, consumers were often forced to purchase twodifferent rotary power tools, a medium-duty tool for “standard”applications such as drilling and fastening, and a heavy-duty toolhaving a low-speed, high torque output for more demanding tasks.

With the advent of the modern high capacity, high voltage battery, it isnow possible to meet the energy demands of a power tool that is used inlow-speed, high torque operations. There remains, however, a need in theart for a power tool transmission having a relatively large range in itsspeed reducing capacity.

SUMMARY OF THE INVENTION

In one form, the present invention provides a power tool having amultiple speed transmission. The power tool has a housing, an electricmotor in the housing having a rotary output shaft that provides a firstoutput torque, a first gear reduction element driven by the rotaryoutput shaft to provide a second output torque, a second gear reductionelement, which is operable in active and inactive modes, driven by thefirst gear reduction element to receive the second output torque and toprovide a third output torque, a third gear reduction element, which isoperable in active and inactive modes, driven by the first gearreduction element to receive the second output torque and to provide afourth output torque, an output spindle operably driven by the secondgear reduction element or the third gear reduction element, and a shiftactuator. The shift actuator has a first position that maintains thesecond and third gear reduction elements in respective inactive modesfor imparting the second output torque to the spindle, a second positionfor maintaining the second gear reduction element in the active mode andthe third gear reduction element in the inactive mode for imparting thethird output torque to the spindle, and a third position for maintainingthe second gear reduction element in the inactive mode and the thirdgear reduction element in the active mode for imparting the fourthoutput torque to the spindle.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional advantages and features of the present invention will becomeapparent from the subsequent description and the appended claims, takenin conjunction with the accompanying drawings, wherein:

FIG. 1 is a side view of a power tool constructed in accordance with theteaching of the present invention;

FIG. 2 is an exploded perspective view of a portion of the power tool ofFIG. 1;

FIG. 3 is a perspective view of a portion of the housing of the powertool of FIG. 1 illustrating the rear of the end cap assembly;

FIG. 4 is a front view of the end cap assembly;

FIG. 5 is a section view taken along the line 5—5 of FIG. 4;

FIG. 6 is a rear view of a portion of the power tool of FIG. 1 with theend cap assembly removed;

FIG. 7 is a side view of a portion of the power tool of FIG. 1 with theend cap assembly removed;

FIG. 8 is a view similar to that of FIG. 4, but illustrating the end capshell prior to the overmolding operation;

FIG. 9 is a view similar to that of FIG. 5, but illustrating the end capshell prior to the overmolding operation;

FIG. 10 is a view similar to that of FIG. 4, but illustrating analternate construction of the overmold member;

FIG. 11 is a partial sectional view of a portion of a power tool thatemploys an end cap assembly having an overmold member constructed in themanner illustrated in FIG. 10;

FIG. 12 is an exploded perspective view of a portion of the power toolof FIG. 1, illustrating the transmission assembly in greater detail;

FIG. 13 is an exploded perspective view of a portion of the power toolof FIG. 1, illustrating the reduction gearset assembly, the transmissionsleeve, a portion of the housing and a portion of the clutch mechanismin greater detail;

FIG. 13 a is a sectional view taken along a longitudinal axis of thesecond ring gear;

FIG. 13 b is a sectional view taken along a longitudinal axis of thethird ring gear;

FIG. 14 is a side view of the transmission sleeve;

FIG. 15 is a rear view of the transmission sleeve;

FIG. 16 is a sectional view taken along the line 16—16 of FIG. 15;

FIG. 17 is a sectional view taken along the line 17—17 of FIG. 15;

FIG. 18 is an exploded view of the reduction gearset assembly;

FIG. 19 is a sectional view taken along a longitudinal axis of the powertool of FIG. 1 illustrating a portion of the reduction gearset assemblyin greater detail;

FIG. 20 is a front view of a portion of the first reduction carrier;

FIG. 21 is a sectional view taken along a longitudinal axis of the powertool of FIG. 1 illustrating a portion of the reduction gearset assemblyin greater detail;

FIG. 22 is a rear view of a portion of the third reduction carrier;

FIG. 23 is an sectional view taken along the longitudinal axis of thepower tool of FIG. 1 and illustrating the transmission assembly aspositioned in the first speed ratio;

FIG. 24 is a sectional view similar to that of FIG. 23 but illustratingthe transmission assembly as positioned in the second speed ratio;

FIG. 25 is a sectional view similar to that of FIG. 23 but illustratingthe transmission assembly as positioned in the third speed ratio;

FIG. 26 is a top view of a portion of the power tool of FIG. 1illustrating the speed selector mechanism in greater detail;

FIG. 27 a is a side view of the rotary selector cam;

FIG. 27 b is a top view of the rotary selector cam;

FIG. 27 c is a sectional view taken through along the central axis ofthe speed selector mechanism;

FIG. 28 is a rear view of the output spindle assembly;

FIG. 29 is an exploded perspective view of the clutch mechanism;

FIG. 29 a is a perspective view of a portion of the clutch mechanismillustrating another configuration of the clutch member;

FIG. 29 b is an exploded perspective view illustrating a multi-piececonstruction for the first ring gear and clutch member;

FIG. 30 is a schematic illustration of the adjustment structure in an“unwrapped” state;

FIG. 31 is a schematic illustration similar to that of FIG. 30 butshowing an alternate construction of the adjustment profile; and

FIG. 32 is a schematic illustration similar to that of FIG. 30 butshowing a portion of another alternate construction of the adjustmentprofile;

FIGS. 33 through 35 are sectional views similar to FIGS. 23 through 25,respectively, taken along the longitudinal axis of a second transmissionconstructed in accordance with the teachings of the present invention;

FIGS. 36 through 38 are sectional views similar to FIGS. 23 through 25,respectively, taken along the longitudinal axis of a third transmissionconstructed in accordance with the teachings of the present invention;

FIGS. 39 through 41 are sectional views similar to FIGS. 23 through 25,respectively, taken along the longitudinal axis of a fourth transmissionconstructed in accordance with the teachings of the present invention;

FIGS. 42 through 44 are sectional views similar to FIGS. 23 through 25,respectively, taken along the longitudinal axis of a fifth transmissionconstructed in accordance with the teachings of the present invention;

FIGS. 45 through 47 are sectional views similar to FIGS. 23 through 25,respectively, taken along the longitudinal axis of a sixth transmissionconstructed in accordance with the teachings of the present invention;

FIGS. 48 through 50 are sectional views similar to FIGS. 23 through 25,respectively, taken along the longitudinal axis of a seventhtransmission constructed in accordance with the teachings of the presentinvention;

FIGS. 51 through 53 are sectional views similar to FIGS. 23 through 25,respectively, taken along the longitudinal axis of an eighthtransmission constructed in accordance with the teachings of the presentinvention; and

FIGS. 54 through 56 are sectional views similar to FIGS. 23 through 25,respectively, taken along the longitudinal axis of a ninth transmissionconstructed in accordance with the teachings of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Overview

With reference to FIGS. 1 and 2 of the drawings, a power toolconstructed in accordance with the teachings of the present invention isgenerally indicated by reference numeral 10. As those skilled in the artwill appreciate, the preferred embodiment of the present invention maybe either a cord or cordless (battery operated) device, such as aportable screwdriver or drill (e.g., drill, hammer drill). In theparticular embodiment illustrated, power tool 10 may be a cordless drillhaving a housing 12, a motor assembly 14, a multi-speed transmissionassembly 16, a clutch mechanism 18, an output spindle assembly 20, achuck 22, a trigger assembly 24 and a battery pack 26. Those skilled inthe art will understand that several of the components of power tool 10,such as the chuck 22, the trigger assembly 24 and the battery pack 26,are conventional in nature and need not be described in significantdetail in this application. Reference may be made to a variety ofpublications for a more complete understanding of the operation of theconventional features of power tool 10. One example of such publicationsis commonly assigned U.S. Pat. No. 5,897,454 issued Apr. 27, 1999, thedisclosure of which is hereby incorporated by reference as if fully setforth herein.

Housing 12 includes an end cap assembly 30 and a handle shell assembly32 that includes a pair of mating handle shells 34. Handle shellassembly 32 includes a handle portion 36 and a drive train or bodyportion 38. Trigger assembly 24 and battery pack 26 are mechanicallycoupled to handle portion 36 and electrically coupled to motor assembly14. Body portion 38 includes a motor cavity 40 and a transmission cavity42. Motor assembly 14 may be housed in motor cavity 40 and includes arotatable output shaft 44, which extends into transmission cavity 42. Amotor pinion 46 having a plurality of gear teeth 46 a may be coupled forrotation with output shaft 44. Trigger assembly 24 and battery pack 26cooperate to selectively provide electric power to motor assembly 14 ina manner that is generally well known in the art so as to control thespeed and direction with which output shaft 44 rotates.

Transmission assembly 16 may be housed in transmission cavity 42 andincludes a speed selector mechanism 60. Motor pinion 46 couplestransmission assembly 16 to output shaft 44, transmitting a relativelyhigh speed, low torque drive input to transmission assembly 16.Transmission assembly 16 includes a plurality of reduction elements thatare selectively engaged by speed selector mechanism 60 to provide aplurality of speed ratios. Each of the speed ratios multiplies the speedand torque of the drive input in a predetermined manner, permitting theoutput speed and torque of the transmission assembly 16 to be varied ina desired manner between a relatively low speed, high torque output anda relatively high speed, low torque output. The transmission output maybe transmitted to the output spindle assembly 20, to which the chuck 22may be coupled for rotation, to permit torque to be transmitted to atool bit (not shown). The clutch mechanism 18 may be coupled totransmission assembly 16 and may be operable for limiting the magnitudeof the torque associated with the drive input to a predetermined,selectable torque limit.

Functional Overmold

With specific reference to FIGS. 2 through 9, end cap assembly 30 mayinclude an end cap shell 100 and an overmold member 102. In the exampleprovided, the end cap shell 100 may be injection molded from a plasticmaterial, such as ABS. The end cap shell 100 defines an end cap cavity104 that may be sized to receive the portion of the motor assembly 14that extends rearwardly of the handle shell assembly 32. A plurality offirst and second radial tab apertures 108 and 110 and an abutting face127 are formed into the forward face 114 of the end cap shell 100 and aplurality of screw bosses 116 are formed into the perimeter of the endcap shell 100. Each of the first and second radial tab apertures 108 and110 may be sized to receive one of the first radial tabs 120 and secondradial tabs 122, respectively, that are formed into the rearward face124 of the handle shells 34. The first and second radial tab apertures108 and 110 cooperate with the first and second radial tabs 122 toproperly align the end cap shell 100 to the handle shell assembly 32, aswell as to inhibit relative rotation therebetween. An arcuate portion128 of the forward face 114 of the end cap shell 100 may be angled tomatch the abutting face 132 of the rearward face 124 of the handleshells 34. The screw bosses 116 permit the end cap shell 100 to befixedly coupled to the motor cover 136 via a plurality of screws 138.The geometry of the motor cover 136 may be such that it is constrainedto the handle shells 34. As such, fastening of the end cap shell 100 tothe motor cover 136 operates to fixedly retain the end cap shell 100against the rearward face 124 of the handle shell assembly 32, as wellas to close off the rear handle aperture 139 in the handle shellassembly 32.

A plurality of side apertures 140 are formed into the sides of the endcap shell 100 to permit air to flow through the handle shell assembly 32and cool the motor assembly 14 in a manner that is well known in theart. A plurality of rear apertures 144 are formed into the rear of theend cap shell 100, with each of the rear apertures 144 including arecessed portion 146 that extends only partially into the outer surface148 of the end cap shell 100 and a through-portion 150 that extendscompletely through the end cap shell 100. A pair of retaining tabs 152are formed to extend from the interior surface 154 of the end cap shell100 inwardly into the end cap cavity 104. A channel 156 may be formedinto the interior surface 154 of the end cap shell 100 and intersectseach of the rear apertures 144 and the retaining tabs 152.

The overmold member 102 may be formed from a resilient material, such asthermoplastic elastomer (e.g., HYTREL® manufactured by E.I. du Pont deNemours and Company) and may be simultaneously formed and coupled to theend cap shell 100 in an injection molding operation. In the particularexample provided, the overmold member 102 includes a plurality of bumpermembers 170, a pair of isolators 172 and a linking member 174. Each ofthe bumper members 170 extends from a point roughly coincident with theinterior surface 154 of the end cap shell 100 to a point rearwardly ofthe outer surface 148 of the end cap shell 100 by about 0.5 mm to about1.5 mm and preferably about 0.75 mm. Construction in this manner permitsthe bumper members 170 to provide a degree of shock absorption whichreduces the likelihood of damaging the end cap shell 100 in the eventthat the tool 10 is dropped. Furthermore, it is sometimes necessary foran operator to apply a relatively high force to the tool 10, as whenemploying a hole saw to drill large diameter holes. In such situations,the operator is inclined to press onto the rear of the tool 10 to applya force that is in-line with the axis of the chuck 22. In suchsituations, the bumper members 170 provide the operator with arelatively soft and comfortable surface which tends to resist slippingas well as attenuate the vibrations that are transmitted to theoperator.

The isolators 172 are formed about the retaining tabs 152 on theinterior surface 154 of the end cap shell 100. In the example provided,each of the isolators 172 includes an annular member 180 that extendsforwardly of the interior surface 154 of the end cap shell 100.Construction in this manner permits the end cap shell 100 to engage theisolators 172 to the outer cylindrical surface 14 a and the rear-surface14 b of the motor housing 14 c to fixedly retain the motor 14 d withinthe motor cover 136. This prevents the components of the motor assembly14 from moving along the longitudinal axis of the tool 10, as well asdampens vibrations that are created during the operation of the motorassembly 14. The linking member 174 may be fixedly coupled to each ofthe bumper members 170 and the isolators 172. The linking member 174provides a flow path through which the resilient material flows duringthe formation of the bumper members 170 and the isolators 172. Thelinking member 174 also interconnects the bumper members 170 and theisolators 172, thereby rendering their removal from the end cap shell100 more difficult.

Those skilled in the art will appreciate that this aspect of the presentinvention may be incorporated into various other positions within thehandle assembly 32 for sealing between two or more components, dampeningvibrations or positioning one component relative to another. One suchexample is illustrated in FIGS. 10 and 11 where the isolators 172 aremodified to extend around the perimeter of a portion of the end capcavity 104 and sealingly contact the rear surface 14 b of the motor 14d. The isolators 172 seal the interface between the end cap shell 100and the motor assembly 14, while the bumper members 170 seal the rearapertures 144 in the end cap shell 100. The space 188 defined by theisolators 172 is then filled with grease or another suitable lubricant,which lubricates a motor armature bearing 190.

Transmission Assembly

With reference to FIG. 12, the transmission assembly 16 may be athree-stage, three-speed transmission that may include a transmissionsleeve 200, a reduction gearset assembly 202 and the speed selectormechanism 60. With additional reference to FIGS. 13 through 17, thetransmission sleeve 200 may include a wall member 210 that defines atransmission bore or hollow cavity 212 into which the reduction gearsetassembly 202 may be disposed. The transmission sleeve 200 includes abody 214 and a base 216. The body 214 of the transmission sleeve 200 maybe fairly uniform in diameter and generally smaller in diameter than thebase 216. The inside diameter of the base 216 may be sized to receivethe cylindrical nose portion 220 of the motor cover 136.

A plurality of raised lands 226 are formed into the base 216. The raisedlands 226 define a plurality of first grooves 228 in the outer surface230 of the base 216 and a plurality of second grooves 232 in the innersurface 234 of the base 216. The first grooves 228 are configured toreceive the alignment ribs 238 that are formed into the inner surface242 of the handle shells 34 to align the transmission sleeve 200 to thehandle shells 34 and inhibit relative rotation between the transmissionsleeve 200 and the housing 12. Preferably, the first grooves 228 andalignment ribs 238 are configured in a manner that the transmissionsleeve 200 can only be assembled to the handle shells 34 in oneorientation (i.e., the configuration of the first grooves 228 andalignment ribs 238 prevents the transmission sleeve 200 from beingrotated 180° out of position relative to the handle shells 34). Thesecond grooves 232 will be discussed in greater detail, below.

The body 214 of the transmission sleeve 200 may include a cylindricalbody portion 246 and a pin housing portion 248. In the particularembodiment illustrated, the cylindrical body portion 246 includes aselector cam guide 250, a plurality of lubricant grooves 252 and firstand second sets of ring engagement teeth 254 and 256, respectively. Theselector cam guide 250 may be generally rectangular in cross section,extending outwardly from the top of the outer surface 258 of the bodyportion 246. The lubricant grooves 252 are formed concentrically aroundthe upper half of the perimeter of the body portion 246. The lubricantgrooves 252 have a depth of about 0.01 inch to about 0.030 inch to holda lubricant, such as grease, on the upper half of the perimeter of thebody portion 246. The operation of the selector cam guide 250 and thelubricant grooves 252 will be discussed in detail, below.

A raised bead 264 segregates the interior of the body portion 246 intofirst and second housing portions 260 and 262, respectively. The firstset of ring engagement teeth 254 are formed onto the inner surface 266of the body portion 246 and extend rearwardly from the raised bead 264toward the base 216. The second set of ring engagement teeth 256 arealso formed into the inner surface of the body portion 246 but extendforwardly from the raised bead 264. The teeth 268 of the first andsecond sets of ring engagement teeth 254 and 256 are uniformly spacedaround the inner surface 266 of the body portion 246. The configurationof each tooth 268 in the first and second sets of ring engagement teeth254 and 256 are similar in that each tooth extends from the raised bead264, has a pair of parallel engagement surfaces 270 and terminates at atip portion 272. The tip portion 272 of each tooth 268 may be bothrounded and tapered to enhance the ability with which it will mesh witha portion of the reduction gearset assembly 202 as will be described indetail, below.

The pin housing portion 248 extends downwardly from the body portion 246over a significant portion of the length of the body portion 246. Anactuator aperture 274 may be formed into the pin housing portion 248 andextends rearwardly through the base 216 of the transmission sleeve 200.In the particular embodiment illustrated, the actuator aperture 274 maybe stepped, having a first portion 276 with a first diameter at the rearof the transmission sleeve 200 and a second portion 278 with a smallersecond diameter at the front of the transmission sleeve 200. In theexample shown, the first portion 276 of the actuator aperture 274 breaksthrough the wall of the first housing portion 260 and forms a groove 280into the inner surface 234 of the base 216. The pin housing portion 248will be discussed in further detail, below.

A pair of first clip slots 284 and a pair of second clip slots 286 areformed into the transmission sleeve 200, extending along the sides ofthe transmission sleeve 200 in a manner that may be parallel thelongitudinal axis of the transmission sleeve 200. The first pair of clipslots 284 may be formed through the sides of the body portion 246rearwardly of the raised bead 264 and extends rearwardly toward the base216. The depth of the first pair of clip slots 284 may be such that theydo not extend through the portion of the wall member 210 that definesthe base 216. The second pair of clip slots 286 are also formed throughthe sides of the body portion 246 beginning forwardly of the raised bead264 and extending through the front face 288 of the transmission sleeve200.

With reference to FIGS. 12, 13, 18 and 23, the reduction gearsetassembly 202 may include a first reduction gear set 302, a secondreduction gear set 304 and a third reduction gear set 306. The first,second and third reduction gear sets 302, 304 and 306 are operable in anactive mode and in the particular example provided, the second and thirdreduction gear sets 304 and 306 may also be operable in an inactivemode. Operation in the active mode causes the reduction gear set toperform a speed reduction and torque multiplication operation, whileoperation of the reduction gear set in an inactive mode causes thereduction gear set to provide an output having a speed and torque thatmay be about equal to the speed and torque of the rotary input providedto that reduction gear set. In the particular embodiment illustrated,each of the first, second and third reduction gear sets 302, 304 and 306are planetary gear sets. Those skilled in the art will understand,however, that various other types of reduction gear sets that are wellknown in the art may be substituted for one or more of the reductiongear sets forming the reduction gearset assembly 202.

As shown, the first reduction gear set 302 may include a first reductionelement or ring gear 310, a first set of planet gears 312 and a firstplanet or reduction carrier 314. The first ring gear 310 may be anannular structure, having a plurality of gear teeth 310 a formed alongits interior diameter. A clutch face 316 may be formed into the outerperimeter of the front face 318 of the first ring gear 310 and will bediscussed in greater detail, below. The first ring gear 310 may bedisposed within the portion of the hollow cavity 212 defined by the base216; the front face 318 of the first ring gear 310 contacts a step 320formed into the transmission sleeve 200, thereby limiting the ability ofthe first ring gear 310 to move forwardly into the hollow cavity 212.

The first reduction carrier 314 may be formed in the shape of a flatcylinder, having plurality of pins 322 that extend from its rearwardface 324. A plurality of gear teeth 314 a are formed into almost theentire outer perimeter of the first reduction carrier 314, with a valley314 b being formed between each pair of adjacent gear teeth 314 a. Dueto the spacing of the gear teeth 314 a, one of the valleys (i.e., valley314 b′) is relatively larger than the remaining valleys 314 b due to theomission of a tooth 314 a in the outer perimeter of the first reductioncarrier 314. In the particular embodiment illustrated, the gear teeth314 a of the first reduction carrier 314 are configured so as not to bemeshingly engagable with the gear teeth 310 a of the first ring gear310.

With specific reference to FIGS. 19 and 20, the profile of the gearteeth 314 a is illustrated in greater detail. As shown, each gear tooth314 a terminates at a gradual radius 326 at the forward face 328 of thefirst reduction carrier 314 but terminates abruptly at the rearward face324 of the first reduction carrier 314. A radius 330 is also formed onthe valleys 314 b between the gear teeth 314 a.

Returning to FIGS. 12, 13, 15, 18 and 23, a first thrust washer 332having a first annular portion 334, a second annular portion 336 and aplurality of retaining tabs 338 may be positioned rearwardly of thefirst reduction gear set 302. The retaining tabs 338 engage the secondgrooves 232 in the base 216 of the transmission sleeve 200 and as such,relative rotation between the first thrust washer 332 and thetransmission sleeve 200 may be inhibited. The inside diameter of thebase 216 may be sized to receive the motor cover 136 and as such, thefront face 340 of the motor cover 136 inhibits the axial movement of thefirst thrust washer 332. The first annular portion 334 contacts the rearface 342 of the first ring gear 310, providing a wear surface andcontrolling the amount by which the first ring gear 310 is able to movein an axial direction. The second annular portion 336 may be spacedaxially apart from the first annular portion 334, extending forwardly ofthe first annular portion 334 to provide a wear surface for the firstset of planet gears 312 that also controls the amount by which they canmove in an axial direction.

The first set of planet gears 312 may include a plurality of planetgears 344, each of which being generally cylindrical in shape, having aplurality of gear teeth 344 a formed into its outer perimeter and a pinaperture 346 formed its their center. Each planet gear 344 may berotatably supported on an associated one of the pins 322 and the firstreduction carrier 314 and may be positioned such that its teeth 344ameshingly engage the teeth 310 a of the first ring gear 310. A raisedportion 348 may be formed into the front and rear face 350 and 352 ofeach planet gear 344 that inhibits the teeth 344 a from rubbing on thefirst reduction carrier 314 and the first thrust washer 332 and creatingdust or chips that would impair the performance of the transmissionassembly 16 and reduce its operating life. As the teeth 46 a of themotor pinion 46 on the output shaft 44 are also meshingly engaged withthe teeth 344 a of the planet gears 344, the motor pinion 46 serves as asun gear for the first reduction gear set 302.

The second reduction gear set 304 may be disposed within the portion ofthe hollow cavity 212 defined by the first housing portion 260 and mayinclude a second sun gear 358, a second reduction element or ring gear360, a second set of planet gears 362 and a second planet or reductioncarrier 364. The second sun gear 358 may be fixed for rotation with thefirst reduction carrier 314. The second sun gear 358 includes aplurality of gear teeth 358 a that extend forwardly of the forward face328 of the first reduction carrier 314.

The second ring gear 360 may be an annular structure, having a pluralityof gear teeth 360 a formed along its interior diameter. The gear teeth360 a may be heavily chamfered at the rear face 366 of the second ringgear 360 but terminate abruptly at the front face 368. More preferably,a heavy radius 369 may be formed onto the rear face 366 and the sides ofeach of the gear teeth 360 a, with the heavy radius 369 being employedrather than the heavy chamfer as the heavy radius 369 on the gear teeth360 a provides for better engagement between the second ring gear 360and the first reduction carrier 314.

A plurality of sleeve engagement teeth 370 are formed into the outerperimeter of the second ring gear 360; the sleeve engagement teeth 370extend forwardly toward the front face 368 of the second ring gear 360and terminate at a tip portion 372 that may be rounded and tapersforwardly and inwardly. An annular clip groove 374 may also formed intothe outer perimeter of the second ring gear 360. In the exampleillustrated, the clip groove 374 may be a rectangular slot having a pairof sidewalls 376. The clip groove 374 will be discussed in greaterdetail, below.

The second reduction carrier 364 may be formed in the shape of a flatcylinder, having plurality of pins 378 that extend from its rearwardface 380. The second set of planet gears 362 may include a plurality ofplanet gears 382. Each planet gear 382 may be generally cylindrical inshape, having a plurality of gear teeth 382 a formed into its outerperimeter and a pin aperture 384 formed its center. Each planet gear 382may be rotatably supported on an associated one of the pins 378 and thesecond reduction carrier 364 may be positioned such that the gear teeth382 a of the planet gears 382 meshingly engage the gear teeth 360 a ofthe second ring gear 360. The gear teeth 358 a of the second sun gear358 are also meshingly engaged with the gear teeth 382 a of the planetgears 382.

The third reduction gear set 306 may be disposed within the portion ofthe hollow cavity 212 defined by the second housing portion 262 and mayinclude a third sun gear 398, a third reduction element or ring gear400, a third set of planet gears 402 and a third planet or reductioncarrier 404. The third sun gear 398 may be fixed for rotation with thesecond reduction carrier 364. The third sun gear 398 includes aplurality of gear teeth 398 a that extend forwardly of the front face406 of the second reduction carrier 364.

The third ring gear 400 may be an annular structure, having a pluralityof gear teeth 400 a formed along its interior diameter. The gear teeth400 a may be heavily chamfered at the front face 412 of the third ringgear 400, but terminate abruptly at the rear face 414. More preferably,a heavy radius 407 may be formed onto the front face 412 and the sidesof each of the gear teeth 400 a, with the heavy radius 407 beingemployed rather than the heavy chamfer as the heavy radius 407 on thegear teeth 400 a provides for better engagement between the third ringgear 400 and the third reduction carrier 404. A plurality of sleeveengagement teeth 418 are formed into the outer perimeter of the thirdring gear 400; the sleeve engagement teeth 418 extend rearward towardthe rear face 414 of the third ring gear 400 and terminate at a tipportion 420 that may be rounded and taper both rearwardly and inwardly.An annular clip groove 422 may also be formed into the outer perimeterof the third ring gear 400. In the example illustrated, the clip groove422 may be a rectangular slot having a pair of sidewalls 424. The clipgroove 422 will be discussed in greater detail, below.

The third reduction carrier 404 may be formed in the shape of a flatcylinder, having plurality of pins 428 that extend from its rearwardface 430. A plurality of gear teeth 404 a are formed into almost theentire outer perimeter of the third reduction carrier 404, with a valley404 b being formed between each pair of adjacent teeth 404 a. Due to thespacing of the teeth 404 a, one of the valleys 404 b (i.e., valley 404b′) is relatively larger than the remaining valleys 404 b due to theomission of a tooth 404 a in the outer perimeter of the third reductioncarrier 404. In the particular embodiment illustrated, the gear teeth404 a of the third reduction carrier 404 are configured so as not to bemeshingly engagable with the gear teeth 382 a of the second planet gears382.

With brief additional reference to FIGS. 21 and 22, the profile of thegear teeth 404 a is illustrated in greater detail. As shown, the rearface 430 of the third reduction carrier 404 may be chamfered and a heavyradius 434 may be formed into each of sides of the teeth 404 a andvalleys 404 b. Each gear tooth 404 a terminates abruptly at the forwardface 436 of the third reduction carrier 404.

Returning back to FIGS. 12, 13, 15, 18 and 23, the third set of planetgears 402 may include a plurality of planet gears 438. Each planet gear438 may be generally cylindrical in shape, having a plurality of gearteeth 438 a formed into its outer perimeter and a pin aperture 440formed through its center. Each planet gear 438 may be rotatablysupported on an associated one of the pins 428 and the third reductioncarrier 404 may be positioned such that the gear teeth 438 a of theplanet gears 438 meshingly engage the gear teeth 400 a of the third ringgear 400. A raised portion 442 may be formed into each of the front andrear faces of the planet gears 438 which inhibits the gear teeth 438 afrom rubbing on the third reduction carrier 404 and creating dust orchips that would impair the performance of the transmission assembly 12and reduce its operating life. A second thrust washer 450 may bedisposed around the third sun gear 398 and the teeth 398 a of the thirdsun gear 398 are meshingly engaged with the gear teeth 438 a of theplanet gears 438. The second thrust washer 450 may include a pluralityof retaining tabs 452 that are configured to engage corresponding tabgrooves 454 (FIG. 13) that are formed in the inner surface 266 of bodyportion 246 of the transmission sleeve 200. The retaining tabs 452 andthe tab grooves 454 cooperate to inhibit relative rotation between thesecond thrust washer 450 and the transmission sleeve 200.

The output spindle assembly 20 may include a transmitting means 458 forcoupling a spindle 460 for rotation with the third reduction carrier 404so as to transmit drive torque from the reduction gearset assembly 202to the chuck 22. Such transmitting means 458 are well known in the artand easily adapted to the transmission assembly of the presentinvention. Accordingly, a detailed discussion of the transmitting means458 need not be included herein.

With reference to FIGS. 13, 13 a, 13 b, 16, 17, 18 and 23 through 28,the speed selector mechanism 60 may be movable between a first position500, a second position 502 and a third position 504 and includes aswitch portion 510 for receiving a speed change input and an actuatorportion 512 for manipulating the reduction gearset assembly 202 inaccordance with the speed change input. The actuator portion 512 may beoperatively coupled to the reduction gearset assembly 202 and moves thesecond and third reduction gear sets 304 and 306 between the active andinactive modes in response to movement of the switch portion 510 betweenthe first, second and third positions 500, 502 and 504. In theparticular embodiment illustrated, the actuator portion 512 includes arotary selector cam 520, a plurality of wire clips 522 and a springmember 523. Each of the wire clips 522 may be formed from a round wirewhich may be bent in the shape of a semi-circle 524 with a pair of tabs526 extending outwardly from the semi-circle 524 and positioned on aboutthe centerline of the semi-circle 524. The semi-circle 524 may be sizedto fit within the clip grooves 374 and 422 in the second and third ringgears 360 and 400, respectively. In this regard, the semi-circle 524neither extends radially outwardly of an associated one of the ringgears (360, 400), nor binds against the sidewalls (376, 424) of the clipgrooves (374, 422). In the example provided, the sidewalls (376, 424) ofthe clip grooves (374, 422) are spaced apart about 0.05 inch and thediameter of the wire forming the wire clips 522 may be about 0.04 inch.

The tabs 526 of the wire clips 522 extend outwardly of the hollow cavity212 into an associated one of the clip slots (284, 286) that may beformed into the transmission sleeve 200. The tabs 526 are long enough sothat they extend outwardly of the outer surface 258 of the body 214 ofthe transmission sleeve 200, but not so far as to extend radiallyoutwardly of the portion of the first clip slots 284 in the base 216 ofthe transmission sleeve 200. Configuration of the wire clips 522 in thismanner facilitates the assembly of the transmission assembly 16,permitting the wire clips 522 to be installed to the second and thirdring gears 360 and 400, after which these assemblies are inserted intothe hollow cavity 212 along the longitudinal axis of the transmissionsleeve 200.

With specific reference to FIGS. 13 and 27 a through 27 c, the rotaryselector cam 520 may include an arcuate selector body 530, a switch tab532 and a plurality of spacing members 534. A pair of first cam slots540 a and 540 b, a pair of second cam slots 544 a and 544 b, a springaperture 546 and a guide aperture 548 are formed through the selectorbody 530. The selector body 530 may be sized to engage the outsidediameter of the body portion 246 of the transmission sleeve 200 in aslip-fit manner. The guide aperture 548 may be generally rectangular inshape and sized to engage the front and rear surfaces of the selectorcam guide 250. The guide aperture 548 may be considerably wider than thewidth of the selector cam guide 250, being sized in this manner topermit the rotary selector cam 520 to be rotated on the transmissionsleeve 200 between a first rotational position, a second rotationalposition and a third rotational position. The selector cam guide 250 andcooperates with the guide aperture 548 to limit the amount by which therotary selector cam 520 can be rotated on the transmission sleeve 200,with a first lateral side of the selector cam guide 250 contacting afirst lateral side of the guide aperture 548 when the rotary selectorcam 520 is positioned in the first rotational position, and a secondlateral side of the selector cam guide 250 contacting a second lateralside of the guide aperture 548 when the rotary selector cam 520 ispositioned in the third rotational position.

Each of the first cam slots 540 a and 540 b may be sized to receive oneof the tabs 526 of the wire clip 522 that is engaged to the second ringgear 360. In the particular embodiment illustrated, first cam slot 540 aincludes a first segment 550, a second segment 552 and an intermediatesegment 554. The first segment 550 may be located a first predetermineddistance away from a reference plane 558 that may be perpendicular tothe longitudinal axis of the rotary selector cam 520 and the secondsegment 552 may be located a second distance away from the referenceplane 558. The intermediate segment 554 couples the first and secondsegments 550 and 552 to one another. The configuration of first cam slot540 b is identical to that of first cam slot 540 a, except that it isrotated relative to the rotary selector cam 520 such that each of thefirst, second and intermediate segments 550, 552 and 554 in the firstcam slot 540 b are located 180° apart from the first, second andintermediate segments 550, 552 and 554 in the first cam slot 540 a.

Each of the second cam slots 544 a and 544 b may be sized to receive oneof the tabs 526 of a corresponding one of the wire clips 522. In theparticular embodiment illustrated, second cam slot 544 a includes afirst segment 560, a second segment 562, a third segment 564 and a pairof intermediate segments 566 and 568. The first and third segments 560and 564 are located a third predetermined distance away from thereference plane and the second segment 562 may be located a fourthdistance away from the reference plane 558. The intermediate segment 566a couples the first and second segments 560 and 562 to one another andthe intermediate segment 568 couples the second and third segments 562and 564 together. The configuration of second cam slot 544 b isidentical to that of second cam slot 544 a, except that it is rotatedrelative to the rotary selector cam 520 such that each of the first,second, third and intermediate segments 560, 562, 564 and 566 and 568 inthe second cam slot 544 b are located 180° apart from the first, second,third and intermediate segments 560, 562, 564 and 566 and 568 in thesecond cam slot 544 a.

With the tabs 526 of the wire clips 522 engaged to the first cam slots540 a and 540 b and the second cam slots 544 a and 544 b, the rotaryselector cam 520 may be rotated on the transmission sleeve 200 betweenthe first, second and third positions 500, 502 and 504 to selectivelyengage and disengage the second and third ring gears 360 and 400 fromthe first and third reduction carriers 314 and 404, respectively. Duringthe rotation of the rotary selector cam 520, the first cam slots 540 aand 540 b and the second cam slots 544 a and 544 b confine the wire tabs526 of their associated wire clip 522 and cause the wire tabs 526 totravel along the longitudinal axis of the transmission sleeve 200 in anassociated one of the first and second clip slots 284 and 286.Accordingly, the rotary selector cam 520 may be operative for convertinga rotational input to an axial output that causes the wire clips 522 tomove axially in a predetermined manner. A lubricant (not specificallyshown) may be applied to the lubricant grooves 252 formed into bodyportion 246 of the transmission sleeve 200 may be employed to lubricatethe interface between the transmission sleeve 200 and the rotaryselector cam 520.

Positioning the rotary selector cam 520 in the first rotational position500 causes the tabs 526 of the wire clip 522 that is engaged to thesecond ring gear 360 to be positioned in the first segment 550 of thefirst cam slots 540 a and 540 b and the tabs 526 of the wire clip 522that is engaged to the third ring gear 400 to be positioned in the firstsegment 560 of the second cam slots 544 a and 544 b. Accordingly,positioning of the rotary selector cam 520 in the first rotationalposition causes the second and third ring gears 360 and 400 to bepositioned in meshing engagement with the second and third planet gears362 and 402, respectively. Simultaneously with the meshing engagement ofthe second and third ring gears 360 and 400 with the second and thirdplanet gears 362 and 402, the sleeve engagement teeth 370 and 418 of thesecond and third ring gears 360 and 400, respectively, are positioned inmeshing engagement with the first and second sets of ring engagementteeth 254 and 256, respectively, to inhibit relative rotation betweenthe second and third ring gears 360 and 400 and the transmission sleeve200 to thereby providing the transmission assembly 16 with a firstoverall gear reduction or speed ratio 570 as shown in FIG. 23. Thoseskilled in the art will understand that the tip portion 272 of the teeth268 of the first and second sets of ring engagement teeth 254 and 256and the tip portions 372 and 420 of the sleeve engagement teeth 370 and418, respectively, are rounded and tapered so as to improve theircapability for meshing engagement in response to axial repositioningalong a longitudinal axis of the transmission assembly 16.

Positioning the rotary selector cam 520 in the second rotationalposition 502 causes the tabs 526 of the wire clip 522 that is engaged tothe second ring gear 360 to be positioned in the first segment 550 ofthe first cam slots 540 a and 540 b and the tabs 526 of the wire clip522 that is engaged to the third ring gear 400 to be positioned in thesecond segment 562 of the second cam slots 544 a and 544 b. Accordingly,positioning of the rotary selector cam 520 in second rotational positioncauses the second ring gear 360 to be in meshing engagement with thesecond planet gears 362 and the third ring gear 400 in meshingengagement with both the third planet gears 402 and the third reductioncarrier 404. Positioning of the rotary selector cam 520 in the secondrotational position 502 also positions the sleeve engagement teeth 370of the second ring gear 360 in meshing engagement with the first set ofring engagement teeth 254 while the sleeve engagement teeth 418 of thethird ring gear 400 are not meshingly engaged with the second set ofring engagement teeth 256. As such, relative rotation between the secondring gear 360 and the transmission sleeve 200 is inhibited, whilerelative rotation between the third ring gear 400 and the transmissionsleeve 200 is permitted to thereby provide the transmission assembly 16with a second overall gear reduction or speed ratio 572 as illustratedin FIG. 24.

Positioning the rotary selector cam 520 in the third rotational position504 causes the tabs 526 of the wire clip 522 that is engaged to thesecond ring gear 360 to be positioned in the second segment 552 of thefirst cam slots 540 a and 540 b and the tabs 526 of the wire clip 522that is engaged to the third ring gear 400 to be positioned in the thirdsegment 564 of the second cam slots 544 a and 544 b. Accordingly,positioning of the rotary selector cam 520 in the third rotationalposition causes the second ring gear 360 to be in meshing engagementwith both the second planet gears 362 and the first reduction carrier314 while the third ring gear 400 in meshing engagement with only thethird planet gears 402. Positioning the rotary selector cam 520 in thethird rotation position 504 also positions the sleeve engagement teeth370 on the second ring gear 360 out of meshing engagement with the firstset of ring engagement teeth 254 and the sleeve engagement teeth 418 onthe third ring gear 400 in meshing engagement with the second sets ofring engagement teeth 256 to permit relative rotation between the secondring gear 360 and the transmission sleeve 200 and inhibit relativerotation between the third ring gear 400 and the transmission sleeve 200to provide the transmission assembly 16 with a third overall gearreduction or speed ratio 574.

In the example shown in FIGS. 13, 27 b and 28, the spring member 523 maybe formed from a flat rectangular piece of spring steel and includes aflattened Z-shaped portion 580 and a raised portion 584. The flattenedZ-shaped portion 580 may be configured to wrap around two reinforcementbars 586 that extend into the spring aperture 546, thereby permittingthe raised portion 584 to be maintained at a predetermined position andalso to transmit a spring force between the rotary selector cam 520 andthe spring member 523. With additional reference to FIG. 28, the raisedportion 584 of the spring member 523 may be sized to engage internalnotches 590 formed in the housing 592 of the output spindle assembly 20.Lands 594 that are circumferentially spaced from the rotary selector cam520 are formed between the notches 590. When the output spindle assembly20 is positioned over the transmission assembly 16 and the speedselector mechanism 60 is positioned in one of the first, second andthird rotational positions 500, 502 and 504, the raised portion 584 ofthe spring member 523 engages an associated one of the notches 590. Theforce that is generated by the spring member 523 when the raised portion584 is moved downwardly toward the rotary selector cam 520 in responseto contact between the raised portion 584 and the land 594 acts toinhibit unintended rotation of the speed selector mechanism 60.Furthermore, placement of the raised portion 584 in a notch 590 providesthe user with a tactile indication of the positioning of the rotaryselector cam 520.

In the particular embodiment illustrated in FIGS. 13 and 27 c, switchportion 510 may include an arcuate band 600 having a raised hollow andrectangular selector button 602 formed therein. The arcuate band 600 maybe formed from a plastic material and may be configured to conform tothe outer diameter of the rotary selector cam 520. The open end of theselector button 602 may be configured to receive the switch tab 532,thereby permitting the switch portion 510 and the rotary selector cam520 to be coupled to one another in a fastenerless manner. The pluralityof spacing members 534 are raised portions formed into the rotaryselector cam 520 that are concentric to and extend radially outwardlyfrom the selector body 530. The spacing members 534 elevate the arcuateband 600 to prevent the arcuate band from contacting the wire tabs 526in the first cam slots 540 a and 540 b. The spacing members 534 may alsobe employed to selectively strengthen areas of the rotary selector cam520, such as in the areas adjacent the first cam slots 540 a and 540 b.

Those skilled in the art will understand that the rotary selector cam520 (i.e., the first cam slots 540 a and 540 b and the second cam slots544 a and 544 b) could be configured somewhat differently so as to causethe second ring gear 360 to meshingly engage both the second planetgears 362 and the first reduction carrier 314 while the third ring gear400 meshingly engages both the third planet gears 402 and the thirdreduction carrier 404. Configuration in this manner provides thetransmission assembly 16 with a fourth overall gear reduction or speedratio.

Those skilled in the art will also understand that selector mechanismsof other configurations may be substituted for the selector mechanism 60illustrated herein. These selector mechanisms may include actuators thatare actuated via rotary or sliding motion and may include linkages, camsor other devices that are well known in the art to slide the second andthird ring gears 360 and 400 relative to the transmission sleeve 200.Those skilled in the art will also understand that as the second andthird ring gears 360 and 400 are independently movable between theactive and inactive modes (i.e., the placement of one of the second andthird ring gears 360 and 400 does not dictate the positioning of theother one of the second and third ring gears 360 and 400), the switchmechanism 60 could also be configured to position the second and thirdring gears 360 and 400 independently of one another.

Clutch Mechanism

In FIGS. 23, 26 and 28 through 30, the clutch mechanism 18 may include aclutch member 700, an engagement assembly 702 and an adjustmentmechanism 704. The clutch member 700 may be an annular structure thatmay be fixed to the outer diameter of the first ring gear 310 and whichextends radially outwardly therefrom. The clutch member 700 may includethe clutch face 316 that may be formed iGGnto the front face 318 of thefirst ring gear 310. The outer diameter of the clutch member 700 may besized to rotate within the portion of the hollow cavity 212 that isdefined by the base 216 of the transmission sleeve 200. With specificbrief reference to FIG. 29, the clutch face 316 of the exampleillustrated is shown to be defined by a plurality of peaks 710 andvalleys 712 that are arranged relative to one another to form a seriesof ramps that are defined by an, angle of about 180°. Those skilled inthe art will understand, however, that other clutch face configurationsmay also be employed, such as a sinusoidally shaped clutch face 316′(FIG. 29 a).

While the first ring gear 310 and the clutch member 700 have beenillustrated as a one piece (i.e., unitarily formed) construction, thoseskilled in the art will understand that they may be constructedotherwise. One such embodiment is illustrated in FIG. 29 b wherein thefirst ring gear 310′ may include an annular collar 1000 and a pluralityof tab apertures 1002. The annular collar 1000 may include a pluralityof ramps 1004 that have dual sloping sides, but is otherwise flat. Thefirst ring gear 310′ is otherwise identical to the first ring gear 310.An annular damper 1008 abuts the annular collar 1000 and includes aplurality of tab members 1010 that engage the tab apertures 1002 in thefirst ring gear 310′ to prevent the damper 1008 from rotating relativeto the first ring gear 310′. The damper 1008 includes a body portion1012 that may be configured to match the contour of the annular collar1000 and as such, includes a plurality of mating ramped portions 1014that are configured to engage each of the ramps 1004. The damper 1008may be formed from a suitable impact dampening material, such as acetyl.The clutch member 700′, which may be an annular member that may beformed from a wear resistant material, such as hardened 8620 steel, maybe disposed over the damper 1008. Like the damper 1008, the clutchmember 700′ includes a plurality of tab members 1020, which lock intothe tab apertures 1002 to prevent rotation relative to the first ringgear 310′, and a plurality of mating ramped portions 1022. The matingramped portions 1022 of the clutch member 700′, however, matingly engagethe mating ramped portions 1014 of the damper 1008. While theconstruction in this manner is more expensive relative to the previouslydescribed embodiment, it is more tolerant of high impact forces that areassociated with the operation of the clutch mechanism 18.

In the particular embodiment illustrated, the engagement assembly 702includes a pin member 720, a follower spring 722 and a follower 724. Thepin member 720 includes a cylindrical body portion 730 having an outerdiameter that may be sized to slip-fit within the second portion 278 ofthe actuator aperture 274 that is formed into the pin housing portion248 of the transmission sleeve 200. The pin member 720 also includes atip portion 732 and a head portion 734. The tip portion 732 may beconfigured to engage the adjustment mechanism 704 and in the exampleshown, is formed into the end of the body portion 730 of the pin member720 and defined by a spherical radius. The head portion 734 may becoupled to the end of the body portion 730 opposite the tip portion 732and may be shaped in the form of a flat cylinder or barrel that is sizedto slip fit within the first portion 276 of the actuator aperture 274.Accordingly, the head portion 734 prevents the pin member 720 from beingurged forwardly out of the actuator aperture 274.

The follower spring 722 may be a compression spring whose outsidediameter may be sized to slip fit within the first portion 276 of theactuator aperture 274. The forward end of the follower spring 722contacts the head portion 734 of the pin member 720, while the oppositeend of the follower spring 722 contacts the follower 724. The endportion 740 of the follower 724 may be cylindrical in shape and sized toslip fit within the inside diameter of the follower spring 722. In thisregard, the end portion 740 of the follower acts as a spring follower toprevent the follower spring 722 from bending over when it is compressed.The follower 724 also includes a follower portion 744 having acylindrically shaped body portion 746, a tip portion 748 and a flangeportion 750. The body portion 746 may be sized to slip fit within thefirst portion 276 of the actuator aperture 274. The tip portion 748 maybe configured to engage the clutch face 316 and in the example shown, isformed into the end of the body portion 746 of the follower 724 anddefined by a spherical radius. The flange portion 750 may be formed atthe intersection between the body portion 746 and the end portion 740.The flange portion 750 may be generally flat and configured to receive abiasing force that may be exerted by the follower spring 722.

The adjustment mechanism 704 may also include an adjustment structure760 and a setting collar 762. The adjustment structure 760 may be shapedin the form of a generally hollow cylinder that may be sized to fit ahousing portion 766 of the output spindle assembly 20. The adjustmentstructure 760 includes an annular face 768 into which an adjustmentprofile 770 may be formed. The adjustment profile 770 includes a firstadjustment segment 772, a last adjustment segment 774, a plurality ofintermediate adjustment segments 776 and a ramp section 778 between thefirst and last adjustment segments 772 and 774. In the embodimentillustrated, a second ramp section 779 is included between the lastintermediate adjustment segment 776 z and the last adjustment segment774. Also in the particular embodiment illustrated, the portion of theadjustment profile 770 from the first adjustment segment 772 through thelast one of the intermediate adjustment segments 776 z is formed as aramp having a constant slope. Accordingly, a follower 780 that iscoupled to the housing portion 766 of the output spindle assembly 20 maybe biased radially outwardly toward the inside diameter of theadjustment structure 760 where it acts against the plurality of detents782 that are formed into the adjustment mechanism 704 (e.g., in thesetting collar 762). The follower 724 and plurality of detents 782cooperate to provide the user of tool 10 with a tactile indication ofthe position of the adjustment profile 770 as well as inhibit the freerotation of the adjustment structure 760 so as to maintain the positionof the adjustment profile 770 at a desired one of the adjustmentsegments 772, 774 and 776.

The setting collar 762 may be coupled to the exterior of the adjustmentstructure 760 and may include a plurality of raised gripping surfaces790 that permit the user of the tool 10 to comfortably rotate both thesetting collar 762 and the adjustment structure 760 to set theadjustment profile 770 at a desired one of the adjustment segments 772,774 and 776. A setting indicator 792 may be employed to indicate theposition of the adjustment profile 770 relative to the housing portion766 of the output spindle assembly 20. In the example provided, thesetting indicator 792 includes an arrow 794 formed into the housingportion 766 of the output spindle assembly 20 and a scale 796 that ismarked into the circumference of the setting collar 762.

During the operation of the tool 10, an initial drive torque istransmitted by the motor pinion 46 from the motor assembly 14 to thefirst set of planet gears 312 causing the first set of planet gears 312to rotate. In response to the rotation of the first set of planet gears312, a first intermediate torque is applied against the first ring gear310. Resisting this torque is a clutch torque that is applied by theclutch mechanism 18. The clutch torque inhibits the free rotation of thefirst ring gear 310, causing the first intermediate torque to be appliedto the first reduction carrier 314 and the remainder of the reductiongearset assembly 202 so as to multiply the first intermediate torque ina predetermined manner according to the setting of the switch mechanism60. In this regard, the clutch mechanism 18 biases the first reductiongear set 302 in the active mode.

The magnitude of the clutch torque is dictated by the adjustmentmechanism 704, and more specifically, the relative height of theadjustment segment 772, 774 or 776 that is in contact with the tipportion 732 of the pin member 720. Positioning of the adjustmentmechanism 704 at a predetermined one of the adjustment segments 772, 774or 776 pushes the pin member 720 rearwardly in the actuator aperture274, thereby compressing the follower spring 722 and producing the aclutch force. The clutch force is transmitted to the flange portion 750of the follower 724, causing the tip portion 748 of the follower 724 toengage the clutch face 316 and generating the clutch torque. Positioningof the tip portion 748 of the follower 724 in one of the valleys 712 inthe clutch face 316 operates to inhibit rotation of the first ring gear310 relative to the transmission sleeve 200 when the magnitude of theclutch torque exceeds the first intermediate torque. When the firstintermediate torque exceeds the clutch torque, however, the first ringgear 310 is permitted to rotate relative to the transmission sleeve 200.Depending upon the configuration of the clutch face 316, rotation of thefirst ring gear 310 may cause the clutch force to increase a sufficientamount to resist further rotation. In such situations, the first ringgear 310 will rotate in an opposite direction when the magnitude of thefirst intermediate torque diminishes, permitting the tip portion 748 ofthe follower 724 to align in one of the valleys 712 in the clutch face316. If rotation of the first ring gear 310 does not cause the clutchforce to increase sufficiently so as to fully resist rotation of thefirst ring gear 310, the first reduction gearset 302 will rotate so asto limit the transmission of torque to the first reduction carrier 314.

Configuration of the clutch mechanism 18 in this manner is highlyadvantageous in that the clutch torque is sized to resist the firstintermediate torque, as opposed to the output torque of the tool 10 thatis generated by the multi-reduction transmission assembly 16 andtransmitted through the chuck 22. In this regard, the clutch mechanism18 may be sized in a relatively small manner, thereby improving theability with which it may be incorporated or packaged into the tool 10.Furthermore, as the speed or gear ratios are changed after or downstream of the first ring gear 310, the clutch mechanism 18 is operableover a relatively large span of output torques. In comparison withconventional clutch mechanisms that operate to limit the output torqueof a transmission, these devices are typically operable over arelatively narrow torque band, necessitating a change in their clutchspring if a considerable shift in the magnitude of the output torque isdesired. In contrast, the clutch mechanism 18 of the present inventioncan accommodate a considerable shift in the magnitude of the outputtorque of the tool 10 by simply operating the transmission assembly 16in a different (i.e., lower or higher) gear ratio.

In the operation of rotary power tools such as tool 10, it is frequentlydesirable to change between two clutch settings, as when the tool 10 isused to both drill a hole and thereafter install a screw in that hole.Accordingly, the adjustment mechanism 704 may be rotated relative to theoutput spindle assembly 20 to position the adjustment mechanism 704 at adesired one of the adjustment segments 772, 774 and 776 to perform thefirst operation and thereafter rotated to a second one of the adjustmentsegments 772, 774 and 776 to perform the second operation. In contrastto the known clutch arrangements, the adjustment mechanism 704 of thepresent invention is configured such that the adjustment structure 760and the setting collar 762 are rotatable through an angle of 360°.Assuming the adjustment structure 760 to be positioned at anintermediate adjustment segment 776 x, rotation of the adjustmentmechanism 704 through an angle of 360° would rotate the adjustmentstructure 760 past the other intermediate adjustment segments 776, aswell as the first and last adjustment segments 772 and 774 and the rampsection 778 such that the adjustment structure 760 would again bepositioned at the intermediate adjustment segment 776 x. The feature isespecially convenient when it is necessary to change the clutch settingbetween a relatively high clutch setting and a relatively low clutchsetting. In this regard, the ramp section 778 permits the setting collar762 (and adjustment structure 760) to be rotated from highest clutchsetting, corresponding to the last adjustment segment, to the lowestclutch setting, corresponding to the first clutch setting, withoutpositioning the clutch mechanism 18 in one of the intermediate clutchsettings. Accordingly, the user of the tool 10 is able to vary theclutch setting from its maximum setting to its minimum setting (and viceversa) by rotating the setting collar 762 a relatively small amount.

While the adjustment profile 770 has been described thus far as having aconstant slope, those skilled in the art will appreciate that theinvention, in its broader aspects, may be constructed somewhatdifferently. For example, the adjustment profile 770′ may be formed suchthat each of the first, last and intermediate adjustment segments 772′,774′ and 776′ is detented as illustrated in FIG. 31. In thisarrangement, the detents 782 in the adjustment structure 760 and thefollower 780 in the housing portion 766 of the output spindle assembly20 are unnecessary as the adjustment segments 772′, 774′ and 776′ willcooperate with the engagement 702 to provide the user of the tool 10with a tactile indication of the position of the adjustment profile770′, as well as inhibit the free rotation of the adjustment structure760.

Another example is illustrated in FIG. 32 wherein the adjustment profile770″ is generally similar to the adjustment profile 770 except that theramp section 779 has been omitted so that the last intermediateadjustment segment 776 z is immediately adjacent the last adjustmentsegment 774.

While the transmission assembly 16 has been described thus far asincluding a three-stage, three speed transmission, those of ordinaryskill in the art will appreciate from this disclosure that theinvention, in its broader aspects, may be constructed somewhatdifferently. For example, another (i.e., fourth) or different speedratio may be provided by operating two of the reduction gear sets (e.g.,both the second and third reduction gear sets 304 and 306) in theinactive mode. Those of ordinary skill in the art will also appreciatefrom this disclosure that the second reduction gear set 304 may beplaced in the inactive mode by coupling the second ring gear 360 to thesecond planet carrier 364 (rather than to the first planet carrier 314)and/or that the third reduction gear set 306 may be placed in theinactive mode by coupling the third ring gear 400 to the second planetcarrier 364 (rather than to the third planet carrier 404).

Other transmission assemblies constructed in accordance with theteachings of the present invention are illustrated in FIGS. 33 through56. Generally speaking, these configurations are similar to that whichis described above and illustrated in detail in FIGS. 23 through 25.Accordingly, similar or corresponding elements of the alternatelyconstructed transmission assemblies are identified by similar referencenumerals as were used to describe the transmission assembly 16.

In the example of FIGS. 33 through 35, the transmission assembly 16-1may include one or more movable elements which may be employed toselectively couple the ring gears 360-1 and 400-1 of the second andthird reduction gear sets 304-1 and 306-1, respectively, to thetransmission sleeve 200-1. The movable elements, which may be pins 2000and 2002, may be housed in the transmission sleeve 200-1 and extendthrough corresponding apertures 2004 and 2006, respectively, in thetransmission sleeve 200-1 and may be translated into and out ofengagement with a respective one of the ring gears (i.e., ring rears360-1 and 400-1). In the example provided, each of the ring gears 360-1and 400-1 includes teeth 370-1 and 418-1, respectively, (similar toteeth 370 and 418, respectively, that are shown in FIG. 23) that arespaced apart by a sufficient distance to receive the pins 2000 and 2002,respectively, therebetween. With the ring gears 360-1 and 400-1 lockedto the transmission sleeve 200-1 as shown in FIG. 33, the transmissionassembly 16-1 operates in a manner that is similar to that which isdescribed in conjunction with FIG. 23, above.

In FIG. 34, the transmission assembly 16-1 is shown in a second overallspeed or gear reduction ratio, wherein the first and second reductiongear sets 302-1 and 304-1 are in an active mode and the third reductiongear set 306-1 is in an inactive mode. The third reduction gear set306-1 may be inactivated by moving (e.g., translating) the pin 2002 outof engagement with the teeth 418-1 of the ring gear 400-1 and engagingthe third planet carrier 404-1 to the third ring gear 400-1. This lattertask may be accomplished, for example, by sliding the third planetcarrier 404-1 toward and into engagement with the third ring gear 400-1.Any appropriate means may be employed to engage the third planet carrier404-1 and the third ring gear 400-1 to one another, including friction(i.e., frictional engagement), or features, such as pins or teeth, thatmay be formed on one or both of the third planet carrier 404-1 and thethird ring gear 400-1. In the example provided, teeth 2010, which areformed on the third ring gear 400-1, engage mating teeth 2012 that areformed on the planet carrier 404-1.

In FIG. 35, the transmission assembly 16-1 is shown in a third overallspeed or gear reduction ratio, wherein the first and third reductiongear sets 302-1 and 306-1 are in an active mode and the second reductiongear set 304-1 is in an inactive mode. The second reduction gear set304-1 may be inactivated by moving (e.g., translating) the pin 2000 outof engagement with the teeth 370-1 of the ring gear 360-1 and engagingthe first planet carrier 314-1 to the second ring gear 360-1.

This latter task may be accomplished, for example, by sliding the firstplanet carrier 314-1 toward and into engagement with the second ringgear 360-1. Any appropriate means may be employed to engage the firstplanet carrier 314-1 and the second ring gear 360-1 to one another,including friction (i.e., frictional engagement), or features, such aspins or teeth, that may be formed on one or both of the first planetcarrier 314-1 and the second ring gear 360-1. In the example provided,teeth 2014, which are formed on the second ring gear 360-1, engagemating teeth 2016 that are formed on the first planet carrier 314-1.

Those skilled in the art will appreciate that although the movableelements (e.g., pins 2000 and 2002) have been illustrated as translatingin a direction that is generally perpendicular to the longitudinal axisof the transmission assembly 16-1, the invention in its broadestaspects, however, may be configured somewhat differently. For example,each of the movable elements may be translated in a direction that isgenerally parallel to the longitudinal axis of the transmission 16-1between a first position, which permits the movable element to engage afeature on a respective one of the ring gears, and a second position,which aligns the movable element to an annular groove or a smooth,featureless portion on the respective ring gear so that the movableelement does not inhibit the rotation of the respective ring gear.

The transmission assembly 16-2 of FIGS. 36 through 38 is generallysimilar to the embodiment of FIGS. 33 through 35, except that the firstset of planet gears 344 of the first reduction gear set 302-2 and thethird set of planet gears 402 of the third reduction gear set 306-2remain in a fixed position relative to the first and third ring gears310 and 400-1, respectively, regardless of the position of the first andthird planet carriers 314-2 and 404-2, respectively. The first planetcarrier 314-2 can be in a rearward position (shown in FIG. 36) when thesecond reduction gear set 304-2 is in an active mode and a forwardposition when the second reduction gear set 304-2 is in an inactivemode. The third planet carrier 404-2 can be in a forward position (shownin FIG. 36) when the third reduction gear set 306-2 is in an active modeand a rearward position (shown in FIG. 37) when the third reduction gearset 306-2 is in an inactive mode. In contrast, the first set of planetgears 344 and the third set of planet gears 402 slide with the first andthird planet carriers 314-1 and 404-1, respectively, in the embodimentof FIGS. 33 through 35.

With reference to FIGS. 39 through 41, the transmission assembly 16-3may include one or more locking elements that may be selectivelyemployed to lock the second and third ring gears 360-3 and 400-3 to thefirst and third planet carriers 314-3 and 404-3, respectively. Thelocking elements may include, for example first and second idler gears2050 and 2052, for example, that may have teeth 2050 a and 2052 a,respectively, that may be meshingly engaged to teeth 314 a and 404 a,respectively, that are formed on the first and third planet carriers314-3 and 404-3, respectively. The locking elements 2050 and 2052 may berotatably supported on pins 2054 and 2056, respectively, that may bemounted to another portion of the power tool, such as the transmissionsleeve 200-3. In a first speed reduction ratio, which is illustrated inFIG. 39, the second and third ring gears 360-3 and 400-3 are fixed tothe transmission sleeve 200-3, for example by teeth 370-3 and 418-3,respectively, on the outer diameter of the ring gears 360-3 and 400-3,respectively, and mating teeth 254-3 and 256-3, respectively, that areformed on the interior of the transmission sleeve 200-3.

In FIG. 40, the transmission assembly 16-3 is shown in a second overallspeed or gear reduction ratio, wherein the first and second reductiongear sets 302-3 and 304-3 are in an active mode and the third reductiongear set 306-3 is in an inactive mode. The third reduction gear set306-3 may be inactivated by translating the third ring gear 400-3 suchthat the teeth 418-3 are not engaged with the mating teeth 256-3 on thetransmission sleeve 200-3 but rather with the teeth 2052 a of the secondidler gear 2052. Translation of the third ring gear 400-3 may also causethe third planet carrier 404-3 to slide on the second idler gear 2052and/or the third set of planet gears 402 to slide relative to thetransmission sleeve 200-3.

In FIG. 41, the transmission assembly 16-3 is shown in a third overallspeed or gear reduction ratio, wherein the first and third reductiongear sets 302-3 and 306-3 are in an active mode and the second reductiongear set 304-3 is in an inactive mode. The second reduction gear set304-3 may be inactivated by translating the second ring gear 360-3 suchthat the teeth 370-3 are not engaged with the mating teeth 254-3 on thetransmission sleeve 200-3 but rather with the teeth 2050 a of the firstidler gear 2050. Translation of the second ring gear 360-3 may alsocause the first planet carrier 314-3 to slide on the first idler gear2050 and/or the first set of planet gears 344 to slide relative to thetransmission sleeve 200-3.

With reference to FIGS. 42 through 44, the transmission assembly 16-4may be configured such that portions of the second reduction gear set304-4 and the third reduction gear set 3064 may slide into and out oflocking engagement with another element of the transmission assembly16-4. In the example provided, the second and third sets of planet gears382-4 and 402-4, respectively, may be translated between a firstposition, in which they meshingly engage an associated ring gear, and asecond position, in which they non-rotatably engage an associated planetcarrier as well as meshingly engage the associated ring gear. In a firstspeed reduction ratio, which is illustrated in FIG. 42, the second andthird ring gears 360-4 and 400-4 are fixed to the transmission sleeve200-4, in a manner that is similar to that which was described above inconjunction with FIG. 33.

In FIG. 43, the transmission assembly 16-4 is shown in a second overallspeed or gear reduction ratio, wherein the first and second reductiongear sets 3024 and 304-4 are in an active mode and the third reductiongear set 306-4 is in an inactive mode. The third reduction gear set306-4 may be inactivated by translating the pin 2002 out of engagementwith the teeth 418-1 on the third ring gear 400-4 and translating thethird set of planet gears 402-4 into engagement with the third planetcarrier 404-4 such that the third set of planet gears 402-4 aremaintained in a stationary condition relative to the third planetcarrier 404-4. Engagement of the third set of planet gears 402-4 to thethird planet carrier 404-4 may be made in any desired manner, such asfrictional engagement or through mating features. In the exampleprovided, teeth 2076 are formed into an axial end face of the third setof planet gears 402-4 and mating teeth 2078 are formed on the thirdplanet carrier 404-4 which meshingly engage the teeth 2076 on the thirdset of planet gears 402-4. The third ring gear 400-4 may optionallytranslate with the third set of planet gears 402-4.

In FIG. 44, the transmission assembly 16-4 is shown in a third overallspeed or gear reduction ratio, wherein the first and third reductiongear sets 302-4 and 306-4 are in an active mode and the second reductiongear set 304-4 is in an inactive mode. The second gear set 304-4 may beinactivated by translating the pin 2000 out of engagement with the teeth370-1 of the second ring gear 360-4 and translating the second set ofplanet gears 382-4 into engagement with the first planet carrier 314-4such that the second set of planet gears 382-4 are maintained in astationary condition relative to the first planet carrier 314-4.Engagement of the second set of planet gears 382-4 to the first planetcarrier 314-4 may be made in any desired manner, such as frictionalengagement or through mating features. In the example provided, teeth2072 are formed into an axial end face of the second set of planet gears382-4 and mating teeth 2074 are formed on the first planet carrier 314-4which meshingly engage the teeth 2072 on the second set of planet gears382-4. The second ring gear 360-4 may optionally translate with thesecond set of planet gears 382-4.

In FIGS. 45 through 47 yet another transmission assembly 16-5constructed in accordance with the teachings of the present invention isillustrated. The transmission assembly 16-5 may include movableelements, such as pins 2000 and 2002, which may be employed to lock thesecond and third ring gears 360-5 and 400-5, respectively, in astationary position, and locking elements, such as first and secondidler gears 2050-5 and 2052-5, respectively, that may be employed tolock each of the second and third ring gears 360-5 and 400-5,respectively, to the first and third planet carriers 314-5 and 404-5,respectively. With specific reference to FIG. 45, the transmission 16-5is illustrated in a first overall speed reduction or gear ratio whereinthe pins 2050-5 and 2052-5 may be positioned in engagement with teeth370-1 and 418-1, respectively, on the second and third ring gears 360-5and 400-5, respectively, to maintain the second and third ring gears360-5 and 400-5 in a stationary position. In this condition, the firstand second idler gears 2050-5 and 2052-5 may be disengaged from theteeth 370-1 and 418-1 of the second and third ring gears 360-5 and400-5, respectively, as well as from the teeth 314 a and 404 a of thefirst and third planet carriers 314-5 and 404-5.

In FIG. 46, the transmission assembly 16-5 is illustrated in a secondoverall speed reduction or gear ratio wherein the first and secondreduction gear sets 302-5 and 304-5, respectively, are in an active modeand the third reduction gear set 306-5 is in an inactive mode. The thirdreduction gear set 306-5 may be inactivated by translating the pin 2002out of engagement with the teeth 418-1 of the third ring gear 400-5 andmoving the idler gear 2052-5, e.g., by translation and/or rotation, intoa position where the teeth 2052 a of the idler gear 2052-5 meshinglyengage both the teeth 418-1 of the third ring gear 400-5 and the teeth404 a of the third planet carrier 404-5.

In FIG. 47, the transmission assembly 16-5 is illustrated in a thirdoverall speed reduction or gear ratio wherein the first and thirdreduction gear sets 302-5 and 306-5 are in an active mode and the secondreduction gear set 304-5 is in an inactive mode. The second reductiongear set 304-5 may be inactivated by translating the pin 2000 out ofengagement with the teeth 370-1 of the second ring gear 360-5 and movingthe idler gear 2050-5, e.g., by translation and/or rotation, into aposition where the teeth 2050 a of the idler gear 2050-5 meshinglyengage both the teeth 370-1 of the second ring gear 360-5 and the teeth314 a of the first planet carrier 314-5.

In FIGS. 48 through 50 yet another transmission assembly 16-6constructed in accordance with the teachings of the present invention isillustrated. The transmission assembly 16-6 may include movableelements, such as idler gears 2050-6 and 2052-6 which may be employed tolock the ring gears 360-6 and 400-6, respectively, into a stationaryposition relative to the transmission sleeve 200-6 or to lock the secondand third ring gears 360-6 and 400-6 for rotation with the first andthird planet carriers 314-6 and 404-6, respectively. With specificreference to FIG. 48, the transmission assembly 16-6 is illustrated in afirst overall speed reduction or gear ratio wherein the idler gears2050-6 and 2052-6 are positioned to maintain the second and third ringgears 360-6 and 400-6 in a stationary position. The idler gears 2050-6and 2052-6 may engage a feature, such as teeth 2090 and 2092,respectively, that is formed on another part of the power tool, such asthe housing 12-6 or the transmission sleeve 200-6, which inhibits theirrotation and thereby locks a respective one of the ring gears in astationary position.

In FIG. 49, the transmission assembly 16-6 is illustrated in a secondoverall speed reduction or gear ratio wherein the first and secondreduction gear sets 302-6 and 304-6 are in an active mode and the thirdreduction gear set 306-6 is in an inactive mode. The third reductiongear set 306-6 may be inactivated by translating the idler gear 2052-6,e.g., along the journal pin 2096, into a position where the teeth 2052 aof the idler gear 2052-6 do not engage the tooth or teeth 2092 butengage both the teeth 418-1 of the third ring gear 400-6 and the teeth404 a of the third planet carrier 404-6.

In FIG. 50, the transmission assembly 16-6 is illustrated in a thirdoverall speed reduction or gear ratio, wherein the first and thirdreduction gear sets 302-6 and 306-6 are in an active mode, and thesecond reduction gear set 304-6 is in an inactive mode. The secondreduction gear set 304-6 may be inactivated by translating the idlergear 2050, e.g., along the journal pin 2096, into a position where theteeth 2050 a of the idler gear 2050-6 do not engage the tooth or teeth2090 but engage both the teeth 370-1 of the second ring gear 360-6 andthe teeth 314 a of the first planet carrier 314-6.

In FIGS. 51 through 53 a further transmission assembly 16-7 constructedin accordance with the teachings of the present invention isillustrated. The transmission assembly 16-7 may include movable,intermediate locking elements, such as collars 3000 and 3002, which maybe employed to lock the second and third ring gears 360-7 and 400-7 in astationary position or for rotation with the first and third planetcarriers 314-7 and 404-7, respectively. With specific reference to FIG.51, the transmission 16-7 is illustrated in a first overall speedreduction or gear ratio wherein the collars 3000 and 3002 are positionedto maintain the second and third ring gears 360-7 and 400-7 in astationary position. The collars 3000 and 3002 may engage the teeth370-1 and 418-1 of the second and third ring gears 360-7 and 400-7 andmay include features, such as teeth or pins 3004 and 3006, respectively,that may engage a mating feature, such as teeth or apertures 3008, thatmay be formed into another portion of the power tool, such as thetransmission sleeve 200-7, to thereby lock a respective one of the ringgears in a stationary position. Alternatively, the pins 3004 and 3006 ofthe collars 3000 and 3002, respectively, may extend through apertures(not shown) that are formed in the second and third ring gears 360-7 and400-7, respectively.

In FIG. 52, the transmission assembly 16-7 is illustrated in a secondoverall speed reduction or gear ratio wherein the first and secondreduction gear sets 302-7 and 304-7 are in an active mode and the thirdreduction gear set 306-7 is in an inactive mode. The third reductiongear set 306-7 may be inactivated by translating the collar 3002 into aposition where the pins 3006 disengage the apertures 3008 in thetransmission sleeve 200-7 and the collar 3002 engages both the teeth418-1 of the third ring gear 400-7 and the third planet carrier 404-7.Any appropriate means may be employed to engage the collar 3002 and thethird planet carrier 404-7 to one another, including friction (i.e.,frictional engagement), or features, such as pins or teeth, that may beformed on one or both of the third planet carrier 404-7 and the collar3002. In the example provided, the collar 3002 frictionally engages theplanet carrier 404-7.

In FIG. 53, the transmission assembly 16-7 is illustrated in a thirdoverall speed reduction or gear ratio wherein the first and thirdreduction gear sets 302-7 and 306-7 are in an active mode and the secondreduction gear set 304-7 is in an inactive mode. The second reductiongear set 304-7 may be inactivated by translating the collar 3000 into aposition where the pins 3004 disengage the apertures 3008 in thetransmission sleeve 200-7 and the collar 3000 engages both the teeth370-1 of the second ring gear 360-7 and the first planet carrier 314-7.Any appropriate means may be employed to engage the collar 3000 and thefirst planet carrier 314-7 to one another, including friction (i.e.,frictional engagement), or features, such as pins or teeth, that may beformed on one or both of the first planet carrier 314-7 and the collar3000. In the example provided, the collar 3000 frictionally engages thefirst planet carrier 314-7.

The embodiment of FIGS. 54 through 56 is generally similar to that ofFIGS. 51 through 53, except that each of the collars 3000-8 and 3002-8includes teeth 3050 and 3052, respectively, that meshingly engage theteeth 370-8 and 418-8, respectively, that are formed on the second andthird ring gears 360-8 and 400-8, respectively. As shown in FIG. 56, thecollar 3000-8 may be translated into a position where the teeth 3050meshingly engage both the teeth 370-8 of the second ring gear 360-8 andthe teeth 314 a of the first planet carrier 314-8 to thereby place thesecond reduction gear set 304-8 into the inactive mode. Similarly, thecollar 3002-8 may be translated into a position where the teeth 3052engage both the teeth 418-8 of the third ring gear 400-8 and the teeth404 a of the third planet carrier 404-8 to thereby place the thirdreduction gear set 306-8 into the inactive mode as is shown in FIG. 55.The first reduction gear set 302-8 is in the active mode in each ofFIGS. 54 through 56.

While the invention has been described in the specification andillustrated in the drawings with reference to various embodiments, itwill be understood by those skilled in the art that various changes maybe made and equivalents may be substituted for elements thereof withoutdeparting from the scope of the invention as defined in the claims.Furthermore, the mixing and matching of features, elements and/orfunctions between various embodiments is expressly contemplated hereinso that one of ordinary skill in the art would appreciate from thisdisclosure that features, elements and/or functions of one embodimentmay be incorporated into another embodiment as appropriate, unlessdescribed otherwise, above. Moreover, many modifications may be made toadapt a particular situation or material to the teachings of theinvention without departing from the essential scope thereof. Therefore,it is intended that the invention not be limited to the particularembodiment illustrated by the drawings and described in thespecification as the best mode presently contemplated for carrying outthis invention, but that the invention will include any embodimentsfalling within the foregoing description and the appended claims.

1. A portable electric rotary power tool having a multiple speedtransmission, the power tool comprising: a housing; an electric motororiented within the housing, the motor having a rotary output shaft forproviding a first output torque; a first gear reduction element operablydriven by the rotary output shaft to receive the first output torque andto provide a second output torque; a second gear reduction elementoperably driven by the first gear reduction element to receive thesecond output torque and to provide a third output torque, the secondgear reduction element having an active mode and an inactive mode; athird gear reduction element operably driven by the first gear reductionelement to receive the second output torque and to provide a fourthoutput torque, the third gear reduction element having an active modeand an inactive mode; an output spindle operably driven by the secondgear reduction element or the third gear reduction element; and a shiftactuator having a first position for maintaining the second and thirdgear reduction elements in respective inactive modes for imparting thesecond output torque to the spindle, a second position for maintainingthe second gear reduction element in the active mode and the third gearreduction element in the inactive mode for imparting the third outputtorque to the spindle, and a third position for maintaining the secondgear reduction element in the inactive mode and the third gear reductionelement in the active mode for imparting the fourth output torque to thespindle; wherein the shift actuator has only one switch member, the onlyone switch member forming a portion of an exterior of the portableelectric rotary power tool and being slidably movable between the firstposition, the second position and the third position, at least onemember of the multiple speed transmission being movable in response tomovement of the only one switch member to cause the first, second andthird gear reduction elements to cooperatively operate in one of atleast three overall speed reduction ratios, each of the overall speedreduction ratios corresponding to an associated one of the first, secondand third positions in which the only one switch member is disposed.